Could use some fleshing out and structuration.
Game dev communities I've been in often list many many photoshop tuts. So why not here. You will be able to take aspects from learning with tuts and apply them to video games. If you got some list em.
Stuff here looked very fun(some nice short tricks)
http://www.greycobra.com/tutorials/photoshop/
This site links to a ton of photoshop tuts.
http://www.tutorialman.com/search.php?search=%20%20%20&page=2
More tuts some videos and resources.
http://www.photoshopsupport.com/tutorials/cs2-photoshop-9.html
Game Related
The pixel sizes for ds2 are 32x32, 64x64, 128x128, 256x256, 512x512 . They can have any mix of these numbers such as 32x64 like you would see in some inventory items.
Seamless Texturing
I use a different technique but could be personal preference. seamless is good for nodes. Cannot seem to find the way I do it.
http://www.gfxartist.com/features/tutorials/740
Some skinning/modelling/painting VTMS
http://www.planetquake.com/polycount/resources/general/video_tutorials/video-tut-list.shtml
Image Bump Mapping
Image Bump Mapping is a great way to get more image quality without a larger file size or memory requirement. Thought I'd post a helpful tutorial I found :P
http://mikegondek.com/creativetech/photoshop/18/psp18.htm
Before
After